1. CHAPTER 11 The Control of Gene Expression
Modules – 11.14

2. 11.12 Cascades of gene expression and cell-to-cell signaling direct the development of an animal
A cascade of gene expression involves genes for regulatory proteins that affect other genes
It determines how an animal develops from a fertilized egg

3. Head of a normal fruit fly Head of a developmental mutant
Mutant fruit flies show the relationship between gene expression and development
Eye
Antenna
Some mutants have legs where antennae should be
Head of a normal fruit fly
Leg
Head of a developmental mutant
Figure 11.12A

4. • Development of head-tail polarity in fruit fly
EGG CELL
WITHIN
OVARIAN
FOLLICLE
Egg cell
Egg protein signaling follicle cells 1
Follicle cells
Gene expression in follicle cells
Follicle cell protein signaling egg cell 2
Localization of “head” mRNA 3
“Head” mRNA
Figure 11.12B

5. FERTILIZATION AND MITOSIS ZYGOTE
EMBRYO
Translation of “head” mRNA
Gradient of regulatory protein 4
Gene expression
Gradient of certain other proteins 5
Gene expression
Body segments 6
Figure 11.12B

6. EMBRYO Body segments 6 LARVA Gene expression ADULT FLY 7 Head end
Tail end
Figure 11.12B

7. Cell-to-cell signaling is important in
Signal-transduction pathways convert messages received at the cell surface into responses within the cell
Cell-to-cell signaling is important in
development
coordination of cellular activities

8. A signal-transduction pathway that turns on a gene
SIGNALING CELL
Signal
molecule 1
Plasma
membrane
Receptor
protein 2
(1) The signaling cell secretes the signal molecule
TARGET CELL
(2) The signal molecule binds to a receptor protein in the target cell’s plasma membrane
Figure 11.13

9. (4) The last relay protein activates a transcription factor
SIGNALING CELL
Signal
molecule 1
Plasma
membrane
Receptor
protein 2
(3) Binding activates the first relay protein, which then activates the next relay protein, etc. 3
TARGET CELL
Relay
proteins 4
Transcription factor (activated)
(4) The last relay protein activates a transcription factor
Figure 11.13

10. (5) The transcription factor triggers transcription of a specific gene
SIGNALING CELL
Signal
molecule 1
Plasma
membrane
Receptor
protein 2
(5) The transcription factor triggers transcription of a specific gene 3
TARGET CELL
Relay
proteins 4
Transcription factor (activated)
(6) Translation of the mRNA produces a protein
NUCLEUS
DNA 5
Transcription
mRNA
New
protein 6
Translation
Figure 11.13

11. 11.14 Key developmental genes are very ancient
Homeotic genes
contain nucleotide sequences called homeoboxes
are similar in many kinds of organisms
arose early in the history of life

12. Fruit fly embryo (10 hours)
Fruit flies and mice have similar homeotic genes (colored boxes)
The order of homeotic genes is the same
The gene order corresponds to analogous body regions
Fly chromosomes
Mouse chromosomes
Fruit fly embryo (10 hours)
Mouse embryo (12 days)
Adult fruit fly
Adult mouse
Figure 11.14